1. Field of the Invention
The present invention relates to a robot vacuum cleaner which autonomously travels, more particularly, to a method for compensating gyro sensor for robot cleaner which detects a rotation angle by using a gyro sensor.
2. Description of the Related Art
Generally, a robot cleaner travels along the outline of cleaning area enclosed with walls or obstacles by using a ultrasonic sensor of a cleaner body to determine a cleaning area or recognize a cleaning area by information input from a user. Then, the robot cleaner plans a traveling path which can efficiently clean the recognized cleaning-area. Finally, the robot cleaner controls a driving part to follow the planned traveling-path, and operates a dust-suction part to perform cleaning.
In order to travel along the planned traveling-path, a robot cleaner calculates a present position by use of an absolute coordinate or a relative coordinate which uses a traveling distance from a reference point of cleaning area and a rotation angle.
As an example of method for traveling by use of an absolute coordinate, a robot cleaner calculates the present position by use of a ceiling image photographed by a CCD camera. In specific, a robot cleaner detects installations such as a lamp, a fluorescent lamp at ceiling from the photographed ceiling image or position recognition marks for a separate position recognition to detect the present position of the robot cleaner, and travels based on the present position. However, the traveling method using CCD camera requires high efficient system and heavy expense for constructions because lots of images should be quickly processed.
A robot cleaner traveling by use of the relative coordinate comprises a traveling distance detection sensor for detecting a traveling distance and an angle sensor for detecting a rotation angle of a robot cleaner. In general, an encoder which can detect a rotation number of traveling wheel is widely used for the traveling distance detection sensor, and a gyro sensor which can detect a relative angle is widely used for the angle sensor. If the gyro sensor is applied, a robot cleaner can turn as desired angles during straight traveling, and therefore, the traveling direction of the robot cleaner can be easily controlled. The gyro sensor, however, has an error of approximate 5˜10% of measured angles. The error is occurred due to a constant error based on integral calculus of gyro sensor and a change of scale factor depending on change of inner variables such as temperature and humidity. In specific, if a rotation of robot cleaner gets greater and the accumulated rotation-angle is great, the error is also accumulated such that a robot cleaner can not follow planned traveling-path. As such, some area is not cleaned enough when a robot cleaner completes traveling along the planned traveling-path.